Code-shaped temperature fuse and sheet-shaped temperature fuse

ABSTRACT

A code type thermal fuse, comprising a fuse core produced by winding a conductor meltable at a predetermined temperature on an insulating core member continuous in the length direction, and an insulating cover covering the outer periphery of the fuse core, wherein the conductor can be cut by expanding the insulating core member at a predetermined temperature and/or by contracting the insulating cover at the predetermined temperature.

TECHNICAL FIELD

The present invention relates to a code type thermal fuse and a sheettype thermal fuse, which can be disconnected when any part thereof isexposed in an abnormal high temperature state, so that the abnormaltemperature can be detected. More particularly, the present inventionrelates to the code type thermal fuse and the sheet type thermal fuse,of which disconnection time is still good even after being deteriorateddue to aging by heat, and which has good operative reliability.

BACKGROUND ART

For example, according to Japanese Unexamined Patent Publication No. Hei6-181028, there has been disclosed a code type thermal fuse, comprisinga space layer and an insulating cover layer around a center core member,on which a conductor meltable at a predetermined temperature is wound inthe lateral direction on an elastic core. There are lead wires connectedto the both ends of the conductor via terminals, and when the conductormelts at excessive temperature the electric connection between the leadwires is cut, whereby the abnormal state is detected.

According to Japanese Unexamined Patent Publication No. Hei 7-306750,there has also been disclosed a code type thermal fuse, substantiallyhaving the same structure.

According to Japanese Unexamined Patent Publication No. 2000-231866,there has been disclosed a code type thermal fuse, wherein a core wire,comprising a metal wire meltable at a predetermined temperature, iswound in the lateral direction with predetermined intervals on a coremember and is inserted into a protection tube. The protection tubecomprises a glass braid sleeve covered by an extruded silicone rubber.

With regard to these code type thermal fuses, to promote the flow of themelted conductor or the metal wire during opening of the fuse, so as toimprove the detecting accuracy, flux was applied to the conductor or themetal wire.

However, according to these types of code type thermal fuses, sincethere have been high-integration of structure of combustion apparatus,the thermal ambience during long-term use becomes severer. Thus, thedeterioration of flux would be prompted due to aging by heat, or thereliability of conductor would be lowered by heat, and it should beforeseen that a quick response to temperature would not be obtainedafter deterioration due to thermal aging.

Although attempts have been made to improve reliability for example,according to the code type thermal fuse of Japanese Unexamined PatentPublication No. 2000-231866, there has been disclosed, as means to solvethe problem, only the silicone rubber material, of which mechanicalstrength is normally low, and which requires reinforcing means as anexterior element. Thus, when the protection tube is ripped and damagedby edges, etc. of metal parts inside the combustion apparatus, therewould be a higher risk of electric leakage by intrusion of water, andalso a higher risk of prompted deterioration of flux due to aging byintrusion of exhaust gas.

In the light of the above problems, it is an object of the presentinvention to provide code type thermal fuse, which can be disconnectedwhen any part thereof is exposed in an abnormal high temperature state,so that the abnormal temperature can be detected accurately, inparticular, of which disconnection time is still good even after beingdeteriorated due to aging by heat, and also to provide a sheet typethermal fuse, substantially having the same characteristic as that ofthe code type thermal fuse as mentioned above.

DISCLOSURE OF INVENTION

To achieve the objects mentioned above, according to claim 1 of thepresent invention, there is provided a code type thermal fusecomprising: a fuse core produced by winding a conductor meltable at apredetermined temperature on an insulating core member continuouslyprovided in the length direction and an insulating cover covering theouter periphery of the fuse core, characterized in that: the conductorcan be cut by expanding the insulating core member at a predeterminedtemperature and/or by contracting the insulating cover at thepredetermined temperature.

According to claim 2 of the present invention, there is provided codetype thermal fuse as claimed in claim 1, further characterized in that:the insulating core member has at least one or more protrusions formedcontinuously or intermittently in the length direction on the outerperiphery of the insulating core member.

According to claim 3 of the present invention, there is provided thecode type thermal fuse as claimed in claim 1 or claim 2, furthercharacterized in that: the insulating cover has at least one or moreprotrusions formed continuously or intermittently in the lengthdirection on the inner periphery of the insulating cover.

According to claim 4 of the present invention, there is provided thecode type thermal fuse as claimed in claim 1, further characterized inthat: another line-shaped or braid-shaped insulator is provided on theinner peripheral side of the insulating cover; and the conductor issandwiched between the insulating core member and the line-shaped orbraid-shaped insulator at least partially in the length direction of theconductor.

According to claim 5 of the present invention, there is provided thecode type thermal fuse as claimed in claim 4, further characterized inthat: the line-shaped or braid-shaped insulator has a characteristic ofcontracting in the length direction around the melting temperature ofthe conductor.

According to claim 6 of the present invention, there is provided thecode type thermal fuse as claimed in claim 4, further characterized inthat: the line-shaped or braid-shaped insulator has a characteristic ofexpanding in the peripheral direction around a melting temperature ofthe conductor.

According to claim 7 of the present invention, there is provided thecode type thermal fuse as claimed in any one claim of claim 1 throughclaim 6, further characterized in that: the insulating core membercomprises a gas-containing material as a structural element.

According to claim 8 of the present invention, there is provided thecode type thermal fuse as claimed in claim 7, further characterized inthat: the insulating core member comprises a gas-containing materialcovering a periphery of a tensile resistant member at the center of theinsulating core member.

According to claim 9 of the present invention, there is provided a sheettype thermal fuse, comprising: the code type thermal fuse according toany one claim of claim 1 through claim 8, provided on a flat surface ina serpentine manner; and means for fixing a layout of the code typethermal fuse.

Accordingly, it is possible to obtain the code type thermal fuse, whichis surely disconnected at abnormal high temperature even at any positionto which any compression force is not applied, and after disconnection,which has no risk of re-contact by melted conductor, etc., whereby anyinappropriate operation is prevented. Further, it is also possible toobtain the sheet type thermal fuse substantially having the samecharacteristic as that of the code type thermal fuse as mentioned above.

The thermal fuse of the present invention may further serve, not onlyfor prevention of deterioration of operative reliability due to lost offlux function under practical using conditions, but also for improvementof operative reliability of aged code type thermal fuse, against such asformation of surface oxide film due to thermal oxidization of conductor.

In addition, the thermal fuse of the present invention is useful,because there is substantially no change of the structure of such athermal fuse as compared with that of conventional thermal fusesassembly, it is also possible to use widely as a safety device forvarious heat apparatus, by not increasing the production cost.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view according to a first embodiment of thepresent invention, in which a part of a code type thermal fuse has beencut off;

FIG. 2 is a sectional view of an elastic core serving as an element ofcode type thermal fuse according to the first embodiment of the presentinvention;

FIG. 3 is a perspective view according to a second embodiment of thepresent invention, in which a part of a code type thermal fuse has beencut off.

FIG. 4 is a perspective view according to a third embodiment of thepresent invention, in which a part of a code type thermal fuse has beencut off.

FIG. 5 is a table according to the first and second embodiments of thepresent invention, showing results of various experiments in regard toexamples 1 through 6, and comparative examples 1 and 2;

FIG. 6 is a perspective view according to a fourth embodiment of thepresent invention, in which a part of a code type thermal fuse has beencut off.

FIG. 7 is a table according to the fourth embodiment of the presentinvention, showing results of various experiments in regard to examples7 through 10;

FIG. 8 is a perspective view according to a fifth embodiment of thepresent invention, in which a part of a code type thermal fuse has beencut off.

FIG. 9 is a sectional view of the code type thermal fuse according tothe fifth embodiment of the present invention;

FIG. 10 is a perspective view according to a sixth embodiment of thepresent invention, in which a part of a code type thermal fuse has beencut off.

FIG. 11 is a perspective view according to a seventh embodiment of thepresent invention, in which a part of a code type thermal fuse has beencut off.

FIG. 12 is a perspective view according to an eighth embodiment of thepresent invention, in which a part of a code type thermal fuse has beencut off.

FIG. 13 is a table according to the fifth, sixth and seventh embodimentsof the present invention, showing results of various experiments inregard to examples 11 through 14;

FIG. 14 is a perspective view according to a ninth embodiment of thepresent invention, in which a part of a code type thermal fuse has beencut off.

FIG. 15 is a perspective view according to a tenth embodiment of thepresent invention, in which a part of a code type thermal fuse has beencut off. and

FIG. 16 is a table according to the ninth and tenth embodiments of thepresent invention, showing results of various experiments in regard toexamples 15 through 18.

BEST MODE FOR CARRYING OUT THE INVENTION

A first embodiment of the present invention will be explained withreference to FIGS. 1, 2 and 5.

There is an elastic core 1 serving as an insulating core member,comprising a gas-containing material as a structural element. There is atensile resistant member 1 a at the center thereof, of which outerperiphery is covered by a gas-containing elastic member 1 b. A conductor3 is wound on the outer periphery of the elastic core 1, and a spacelayer 5, comprising a glass braid, is provided on the outer peripheralside of the conductor 3. Further, an insulating cover 7 covers the outerperiphery of the space layer 5.

For reference, as illustrated in FIG. 2, although the tensile resistantmember 1 a is actually composed of a plurality of fiber bundles, FIG. 1shows them in a single circular shape as a typical model.

The elastic core 1 and the conductor 3 serve as a fuse core 9. Asillustrated in FIG. 2, there are several airtight spaces 11 inside theelastic member 1 b of the elastic core 1, and gas 13 is included in eachairtight space 11.

The tensile resistant member 1 a has a function to improve the tensilestrength and flexibility of a code type thermal fuse, and it is possibleto use any known textile material as a practical material thereof.

The elastic member 1 b is composed of ordinary elastomer material, etc.,having the airtight spaces 11, of which respective shapes aredelomorphous or amorphous, preferably at least any part in the inside ofthe elastic member 1 b. It is possible to use, for example, foamedelastic material having isolated air holes, partially foamed elasticmaterial, or elastic material having continuous holes in the lengthdirection so that the airtight spaces 11 may be formed in thepost-process.

The elastic member 1 b as discussed above may be formed by any knownmethod. There are various methods, for example, such as that theelastomer material serving as the elastic member 1 b has been mixed withorganic foaming agent or inorganic foaming agent, and the mixture isheated and, thus foamed, whereby the foamed elastic member havingisolated air holes can be formed. Further, it is also possible to useother methods, such as forming of foamed elastic member by including gasduring extrusion molding of elastomer material, or forming of partiallyfoamed elastic member by adding sublimation material powder throughheat-aging to elastomer material, or forming of the airtight spaces 11,by preliminarily preparing elastic member having continuous holes in thelength direction during contour extrusion of elastomer material, and inthe post-process, by closing the continuous holes in the lengthdirection at predetermined intervals through use of winding tension ofthe conductor 3.

The cross-sectional shape of the elastic core 1 is not limited inparticular, but it is preferable, as illustrated in FIG. 2, to provide across-sectional shape having a plurality (in the present embodiment,six) of protrusions 15 in the radial directions. This shape may be anypolygon, or any starlike shape. Further, although polygonal shape orstarlike shape has definite corners in general, the corners may also bein depressed and round shape. According to these cross-sectional shapes,compared with the circular cross-sectional shape, the conductor 3 candig into the elastic core 1 easily, and it is preferable, because theconductor 3 may be cut immediately when the elastic core 1 is melted.When the cross-sectional shape is polygon, it is preferable to selecthexagon or less, because of easy digging of the conductor 3.

As for the conductor 3, it is possible to use, for example, metal thinwire selected from the group of low-melting point alloys and solder, orwire formed from conductive resin manufactured by filling high-densitymetal powder, metal oxide or carbon black, into thermoplastic resin suchas olefin resin or polyamide resin. The preferable wire diameter of theconductor 3 is substantially from 0.04 mm to 0.8 mm, because an ordinarywinding machine can wind such a conductor 3 around the elastic core 1 inthe length direction.

It is also possible to apply flux to the conductor 3. The flux may beincluded in the center of the conductor 3, or the flux may be coated onthe surface of the conductor 3. It is possible to use ordinary rosinflux, or it is also possible to use flux having a small volume ofactivator.

The conductor 3 has been wound around the elastic core 1 by applyingtension, so that the conductor 3 may not at least be loose, thus thefuse core 9 is prepared. The each interval of winding the conductor 3is, preferably, not less than one and half of the wire diameter, andmore preferably, not less than twice and not more than 15 times. It isalso possible to provide collective winding in the length direction bywinding the parallel conductors 3 or by winding the stranded conductors3.

The thus obtained fuse core 9 is covered by the insulating cover 7 viathe space layer 5, whereby the code type thermal fuse according to thepresent embodiment is completed.

As there are various known methods in regard to the insulating cover 7,it is possible to select any appropriate method from them, which canrealize the working temperature lower than the melting temperature ofthe conductor 3. It is possible to use the method, for example, in whicha thermoplastic polymer such as ethylene copolymer workable atrelatively low temperature, or a composition of chiefly comprisingsynthetic rubber such as ethylene propylene rubber, styrene butadienerubber, butadiene rubber isoprene rubber or nitrile rubber, iscross-linked by using low-temperature cross-linking method such asradiation cross-linking or Silane cross-linking. Further, it is alsopossible to use a forming method by using silicone rubber which can beextruded around normal temperature and which can be cross-linked atrelatively low temperature, or a forming method, in which, aftercovering by braid of any textile material, the insulating varnish,parched at normal temperature, is coated. In particular, when thesilicone rubber is used, it is also possible to provide a braid asexterior element in order to reinforce the mechanical strength of theinsulating cover 7. The insulating cover 7 may be provided, not only bythe extrusion method as discussed above, but also by first forming atubular insulating cover 7 separately, and thereafter, by inserting thefuse core 9 provided with the space layer 5. The insulating cover 7 maybe preferably thin, because of the increasing heat sensitivity, as longas the required characteristics such as the electric insulation abilityand mechanical strength are satisfied.

Preferably, the insulating cover 7 is not in tight contact with the fusecore 9, but covering with having the space layer 5 as discussed in thepresent embodiment. This is because, by providing the space layer 5, there-connection of the conductor 3 after detecting abnormal temperaturemay be prevented more effectively, and at the same time, the conductor 3may be protected against the heat while the insulating cover 7 isprovided.

The space layer 5 may be formed by any known method, for example, inwhich the insulating cover 7 is provided around the fuse core 9 throughtubing extrusion, or in which an insulating cover provided withprotrusions on the inner periphery thereof is extruded in order to coveraround the fuse core 9, or in which a spacer is provided. These methodsare disclosed in detail, in Japanese Unexamined Patent Applications Nos.Hei 5-128950, Hei 6-181028, Hei 7-176251, Hei 9-129120 and Hei10-223105, all of which were filed by the applicant of the presentinvention. Thus, any of these methods may be used.

Now several examples according to the first embodiment will beexplained.

EXAMPLE 1

The elastic core 1 was manufactured by the following methods. First,silicone varnishing was applied to a glass code having the outerdiameter of about 0.7 mm, thus the tensile resistant member 1 a wasprovided. Thereafter, a silicone rubber, comprising a compound of 100w/t parts (part by weight) of silicone rubber, 1 w/t part of foamingagent (AIBN) and 2 w/t parts of organic peroxide cross-linking agentkneaded on open roll, was extruded in order to cover the periphery ofthe tensile resistant member 1 a, so that the cross-section of thesilicone rubber had six radial protrusions, of which inscribed circlewas 1.6 mm and of which circumscribed circle was 1.8 mm. At the sametime, the silicone rubber was foamed by applying hot-air vulcanization.Thus, the foamed elastic member 1 b, having isolated air holes, wasformed.

Thereafter, two parallel conductors 3, respectively comprising 0.6 mm φof eutectic solder wire (melting temperature at 183° C.) in which fluxhad been included at the center, were drawn at the same tension andwound at an interval of 8.5 mm in the length direction around thecorners of the elastic core 1. Then, non-alkali glass filaments, each ofwhich fiber diameter was about 9 μm, were stranded together in order toobtain a fiber bundle (yarn number: around #70), and this fiber bundlewas braided by 16-yarn string manufacturing machine (using 16 yarns formanufacturing a single string), at braid coverage of about 17/25 mm,thus the space layer (glass braid) 5 was obtained. As the final step, amixture of ethylene copolymer, serving as the insulating cover 7, wasextruded to form the cover at thickness of 0.5 mm and at extrusiontemperature of 150° C., and thereafter, the cross-linking was done byapplying electron beam thereto.

The thus obtained code type thermal fuse was cut at length of about 20cm, and the insulating cover 7 and the space layer (glass braid) 5 ateach end were removed for about 1 cm respectively. Then, lead wireshaving the nominal cross-sectional area of 0.5 mm², each of which was atlength of 100 mm, were connected via crimp-type terminals, thus the codetype thermal fuse assembly was manufactured.

Then, Experiments 1 and 2 were respectively done for the thus obtainedcode type thermal fuse, as follows:

Experiment 1: Initial Operative Temperature

Experiment Method:

The code type thermal fuse assembly manufactured by the above method wasinserted in a glass fiber braid tube at inner diameter of 4.0 mm and atlength of about 15 cm, so that the code type thermal fuse part of theassembly may come to the center part of the tube. Thereafter, anelectric current about 0.1 A was applied from 100 V AC power supply, byconnecting incandescent bulb to the both terminals of the lead wires asan outer load. Then, the center part was heated from normal temperature,at temperature increase speed of 10° C./min. Thus, when the conductor 3was disconnected, the temperature was checked.

Experiment 2: Operative Temperature After Lost of Flux

Experiment Method:

The manufactured code type thermal fuse assembly was placed in a hot-aircirculation type of constant-temperature bath at temperature of 158° C.,for 384 hours, whereby the deterioration due to aging by heat wasprompted, and the flux was decomposed and removed by heat. Thereafter,the code type thermal fuse assembly after heat treatment was inserted ina glass fiber braid tube at inner diameter of 4.0 mm and at length ofabout 15 cm, so that the code type thermal fuse part of the assembly maycome to the center part of the tube. Thereafter, an electric currentabout 0.1 A was applied from 100 V AC power supply, by connectingincandescent bulb to the both terminals of the lead wires as an outerload. Then, the center part was heated from initial temperature of 250°C., at temperature increase speed of 10° C./min. Thus, when theconductor 3 was disconnected, the temperature was checked.

The results of Experiments 1 and 2 are shown in FIG. 5.

EXAMPLE 2

The tensile resistant member 1 a, having isolated air holes, was formedby using silicone rubber to which 2 w/t parts of foaming agent (AIBN)were added. The other materials and manufacturing method weresubstantially the same as those of Example 1, thus the code type thermalfuse was manufactured. Then the experiments, substantially the same asthose of Example 1, were done for this code type thermal fuse, of whichresults are also included in FIG. 5.

EXAMPLE 3

As for the conductor 3, 0.6 mm φ of eutectic solder wire withoutincluding flux was used. The other materials and manufacturing methodwere substantially the same as those of Example 1, thus the code typethermal fuse was manufactured. Then the experiments, substantially thesame as those of Example 1, were done for this code type thermal fuse,of which results are also included in FIG. 5.

EXAMPLE 4

The tensile resistant member 1 a was prepared by a glass code having theouter diameter of about 0.7 mm, to which silicone varnishing was notapplied. Thereafter, a silicone rubber, comprising a compound of 100 w/tparts of silicone rubber, 3 w/t parts of polyacetal homopolymer powder(particles passed through 100-mesh sieve) and 2 w/t parts of organicperoxide cross-linking agent kneaded on open roll, was extruded in orderto cover the periphery of the tensile resistant member 1 a, so that thecross-section of the silicone rubber had six radial protrusions, ofwhich inscribed circle was 1.6 mm and of which circumscribed circle was1.8 mm. At the same time, hot-air vulcanization was applied, thus theelastic member 1 b was formed. The subsequent steps were substantiallythe same as those of Example 1, and the code type thermal fuse wasmanufactured. The elastic core 1 at this stage was a silicone rubberelastic core including scattered polyacetal homopolymer powders, andthere was no air hole in the inside thereof.

Then, Experiment 1 as discussed above was done for the code type thermalfuse in this state.

Thereafter, the code type thermal fuse assembly was manufacturedsubstantially by the same method as that of Example 1. Then, themanufactured code type thermal fuse assembly was placed in a hot-aircirculation type of constant-temperature bath at temperature of 158° C.,for 384 hours, whereby the deterioration due to aging by heat wasprompted, thus the state after deterioration due to aging wasreproduced. At this stage, the polyacetal homopolymer powder had beensublimed by heat, whereby the foamed elastic member 1 b having isolatedair holes was formed.

With reference to this Example, the code type thermal fuse in this statewas heated from temperature of 300° C., at temperature increase speed of10° C./min, and the disconnected temperature was checked as results ofExperiment 2. Then the results of Experiment 1 and Experiment 2 werealso included in FIG. 5.

EXAMPLE 5

As the insulating cover, instead of using mixture of ethylene copolymer,mixture of ethylene propylene rubber was used, which was then extrudedat temperature of 130° C. in order to form the cover. The othermaterials and manufacturing method were substantially the same as thoseof Example 1, thus the code type thermal fuse was manufactured. Then theexperiments, substantially the same as those of Example 1, were done forthis code type thermal fuse, of which results are also included in FIG.5.

COMPARATIVE EXAMPLE 1

The elastic core was formed by using silicone rubber to which no foamingagent was added, and 0.6 mm φ of eutectic solder wire without includingflux was used as the conductor. The other materials and manufacturingmethod were substantially the same as those of Example 1, thus the codetype thermal fuse was manufactured. Then the experiments, substantiallythe same as those of Example 1, were done for this code type thermalfuse, of which results are also included in FIG. 5.

COMPARATIVE EXAMPLE 2

The elastic core was formed by using silicone rubber to which no foamingagent was added, and 0.6 mm φ of eutectic solder wire including flux atthe center thereof was used as the conductor. The other materials andmanufacturing method were substantially the same as those of Example 1,thus the code type thermal fuse was manufactured. Then the experiments,substantially the same as those of Example 1, were done for this codetype thermal fuse, of which results are also included in FIG. 5.

According to results of FIG. 5, it is understood that the initialoperative temperature of each Example is the melting temperature of theconductor 3 (183° C.).

With reference to the operative temperature after the lost of flux, itis understood that, as compared with the operative temperature of theconventional code type thermal fuse (Comparative Example 2), that of thecode type thermal fuse according to the present embodiment, of whichelastic core 1 is comprising, the tensile resistant member 1 a, and theelastic member 1 b covering around the tensile resistant member 1 a andincluding the air, becomes lower. Further, with reference to Examples 2and 4 having more isolated air holes, as compared with Examples 1 and 5,the operative temperature becomes still lower.

With reference to the code type thermal fuse of Example 3, using theconductor 3 to which the flux application was not done, as compared withthe code type thermal fuses of Examples 1, 2, 4 and 5, the operativetemperature becomes higher. It is considered that, the reason will bebecause of larger conductor area rate of the conductor 3 as comparedwith that of the non-flux conductor. Similarly, it is understood that,as compared with the code type thermal fuse, the operative temperaturebecomes higher.

Now a second embodiment of the present invention will be explained withreference to FIG. 3. According to the second embodiment, with referenceto the first embodiment, the space layer (glass braid) 5 has beenremoved.

The other structure is substantially the same as that of the firstembodiment as discussed above, and the identical numerals are allottedto the identical elements, and the explanation thereof will not be made.

With reference to the second embodiment, substantially the sameexperiments as those of Experiments 1 and 2 were done as Example 6, andthe results are also included in FIG. 5.

According to results of FIG. 5, it is understood that the initialoperative temperature is the melting temperature of the conductor 3(183° C.).

With reference to the operative temperature after the lost of flux, itis understood that, as compared with the operative temperature of theconventional code type thermal fuse (Comparative Example 2, as discussedabove), that of the code type thermal fuse according to the presentembodiment, of which elastic core 1 is comprising, the tensile resistantmember 1 a, and the elastic member 1 b covering around the tensileresistant member 1 a and including the air, becomes lower.

Now a third embodiment of the present invention will be explained withreference to FIG. 4. As illustrated in FIG. 4, a sheet type thermal fusewas manufactured, by placing the code type thermal fuse according to thefirst embodiment as discussed above, in a serpentine manner by anymethod such as that disclosed in Japanese Unexamined Patent PublicationNo. Sho 62-44394. Reference numeral 21 shows a double-faced adhesivepaper, having a peeling paper 23 on one side. Reference numeral 25 showsthe sheet type thermal fuse, positioned in a serpentine manner on theupper surface of the double-faced adhesive paper 21. Further, referencenumeral 27 shows a metal foil covering the whole part of the sheet typethermal fuse 25, and the metal foil 27 has been adhered to and fixed onthe double-faced adhesive paper 21.

An acrylic adhesive paper is used as the double-faced adhesive paper 21,and an aluminum foil at thickness of 100 μ m is used as the metal foil27.

Since the present embodiment was provided according to JapaneseUnexamined Patent Publication No. Sho 62-44394, the metal foil 27 andthe double-faced adhesive paper 21 are used. However, it is possible tomanufacture by not referring to this Unexamined Patent Publication, orit is also possible to use other material, such as a plastic filminstead of the metal foil.

The thus manufactured sheet type thermal fuse was attached to an ironpanel at thickness of 0.5 mm, and the panel was placed in uprightposition. A commercially available wall paper was attached to thereverse side of the panel. In this state, 0.5 A of electric current wasapplied to the sheet type thermal fuse, and a burner was moved closer sothat the burner flame was in contact with the panel. This state wasmaintained until the conductor of the thermal fuse was disconnected.Thereafter, the sheet type thermal fuse detected the heat, and wasdisconnected. After disconnection, there was no change, such ascarbonization of the wall paper on the reverse side of the panel, and itwas found that the thermal fuse expressed the effective performance.

Now a fourth embodiment of the present invention will be explained withreference to FIGS. 6 and 7. According to the present embodiment, aninsulating core member 101 has a tensile resistant member 101 a at thecenter, around which is covered by a polymer elastic member 101 bincluding the air. A conductor 3 is wound around the insulating coremember 101. Thus, the insulating core member 101 and the conductor 3serve as a fuse core 105. Further, the fuse core 105 is covered by aninsulating cover 107. The insulating cover 107 has at least one or more(in the present embodiment, six) protrusions 109, formed continuously orintermittently on the inner surface in the length direction.

The insulating core member 101 is formed by any material, havingcharacteristic of being not melted around the melting temperature of theconductor 103, and also characteristic of expanding in thecircumferential direction, for example, any metal wire to whichinsulation process has been applied, such as an electric wire in whichthermoplastic polymer or thermoset polymer has been extruded on aconductor, or cable material comprising any polymer which has beenformed by plastic extrusion of synthetic fiber, thermoplastic polymer orthermoset polymer, or any inorganic material such as ceramic fiber orglass fiber. Any one of the above materials may be used as a singlematerial, but it is also possible to use a plurality of materials byapplying the same tension thereto, or by stranding together, or bypreparing composite material through combination of different materialtypes.

As discussed above, among these materials according to the presentembodiment, with reference to the structure in which the tensileresistant member 101 a at the center is covered by the polymer elasticmember 101 b including the air, it is possible to reinforce themechanical strength appropriately, and at the same time, it is alsopossible to arbitrarily control the degree of expansion of the polymerelastic member 101 b including the air.

The tensile resistant member 101 a may be used for the purpose ofimproving the tensile strength and flexibility of the code type thermalfuse obtained by the present embodiment. The tensile resistant material101 a may be formed by using any known textile material.

The polymer elastic member 101 b including the air as discussed has thestructure that delomorphous or amorphous airtight spaces have beenformed, preferably at least any part in the inside of the elasticmaterial comprising ordinary elastomer material, for example, siliconerubber, ethylene propylene rubber, natural rubber, isoprene rubber,acrylic rubber, fluorocarbon rubber, ethylene-vinyl acetate copolymer(EVA), ethylene-ethyl acrylate copolymer resin (EEA), or anythermoplastic elastomer (TPE). It is possible to use, for example,foamed elastic material having isolated air holes, partially foamedelastic material, or elastic material having continuous holes in thelength direction so that the airtight spaces may be formed in thepost-process.

The elastic member 101 b as discussed above may be formed by any knownmethod. There are various methods, for example, such as that theelastomer material serving as the elastic member has been mixed withorganic foaming agent or inorganic foaming agent, and the mixture isheated and thus foamed, whereby the foamed elastic member havingisolated air holes can be formed. Further, it is also possible to useother methods, such as forming of foamed elastic member by including gasduring extrusion molding of elastomer material, or forming of partiallyfoamed elastic member by adding sublimation material powder throughheat-aging to elastomer material, or forming of the airtight spaces, bypreliminarily preparing elastic member having continuous holes in thelength direction during contour extrusion of elastomer material, and inthe post-process, by closing the continuous holes in the lengthdirection through use of winding tension of the conductor, which will beexplained afterwards.

As for the conductor 103, it is possible to use, for example, metal thinwire selected from the group of low-melting point alloys and solder, orwire formed from conductive resin manufactured by filling high-densitymetal powder, metal oxide or carbon black, into thermoplastic resin suchas olefin resin or polyamide resin. The preferable wire diameter of theconductor 103 is substantially from 0.04 mm to 2.0 mm, because anordinary winding machine can wind such a conductor 103 around theelastic core in the length direction.

The conductor 103 has been wound around the insulating core member 101by applying tension, so that the conductor 103 may not at least beloose, thus the fuse core 105 is prepared. It is more preferable toselect the polymer elastic member 101 b including the air as theinsulating core member 101, because the conductor 103 may dig into theinsulating core member 101 sufficiently. The each interval of windingthe conductor 103 is, preferably, not less than one and half of the wirediameter, and more preferably, not less than twice and not more than 15times. It is also possible to provide collective winding in the lengthdirection by winding the paralleled conductors 3 or by winding thestranded conductors 103.

The thus obtained fuse core 105 is covered by the insulating cover 107,whereby the code type thermal fuse according to the present embodimentis completed. As discussed above, according to the present embodiment,the insulating cover 107 has at least one or more (in the presentembodiment, six) protrusions 109, formed continuously or intermittentlyon the inner surface in the length direction. The protrusions 109 havebeen provided because of the following reason.

This is because, when the insulating core member 101 is heated by anyabnormal state and expanded in the circumferential direction, theconductor 103 wound around the insulating core member 101 is pressedbetween the insulating core member 101 and the protrusions 109 providedon the inner periphery of the insulating cover 107, whereby theconductor 103 may be disconnected more surely by pressure during meltingor just before melting thereof.

The protrusions 109 have further merits. As a predetermined space may beformed between the fuse core 105 and the insulating cover 107, after theconductor 103 is disconnected by detecting abnormal temperature, it ispossible to prevent re-connection of the conductor 3 by re-heating moreeffectively.

As there are various known methods in regard to the insulating cover107, it is possible to select any appropriate method from them, whichcan be worked at lower temperature than the melting temperature of theconductor 103. It is possible to use the method, for example, in which athermoplastic polymer such as ethylene copolymer workable at relativelylow temperature, or a synthetic rubber such as ethylene propylenerubber, styrene butadiene rubber, isoprene rubber or nitrile rubber, iscross-linked by using low-temperature cross-linking method such asradiation cross-linking. Further, it is also possible to use a formingmethod by using silicone rubber which can be extruded around normaltemperature and which can be cross-linked at relatively low temperature.In particular, when the silicone rubber is used, it is also possible toprovide a braid as exterior element in order to reinforce the mechanicalstrength of the insulating cover 107. The insulating cover 107 may beprovided, not only by the extrusion method as discussed above, but alsoby first forming a tubular insulating cover 107 separately, andthereafter, by inserting the fuse core 105. The insulating cover 107 maybe preferably thin, because of the increasing heat sensitivity, as longas the required characteristics such as the electric insulation abilityand mechanical strength are satisfied. It is preferable that the size ofeach protrusion 109 protruding in the circumferential direction issmaller because of the increasing heat sensitivity, as long as therequired characteristic in order to prevent the re-connection issatisfied.

According to the present embodiment, when the temperature increases, theinsulating core member 101 is expanded in the circumferential direction,and presses the conductor 103 toward the protrusions 109 on the innerperiphery of the insulating cover 107, whereby the conductor 103 may bedisconnected more surely during melting or just before melting thereof.Thus, even when the original function of flux (the function to improvethe detecting accuracy) is deteriorated, it is still possible tomaintain the good disconnection time. Further, it is still effectiveeven when any deterioration, such as forming of oxide, appears on thesurface of the conductor 103 due to long-term use thereof and themelting disconnection cannot be done easily. As the structure of partsis not changed from conventional structure, and no complicated structureis required. Thus, it is possible to provide cost-effective products.

Now several examples according to the present embodiment will beexplained.

EXAMPLE 7

First, silicone varnishing was applied to a glass code having the outerdiameter of about 0.7 mm, thus the tensile resistant member 101 a wasprovided. Thereafter, a silicone rubber, comprising a compound of 100w/t parts of silicone rubber, 1 w/t part of foaming agent (AIBN) and 2w/t parts of organic peroxide cross-linking agent kneaded on open roll,was extruded in order to cover the periphery of the tensile resistantmember 101 a, so that the cross-section of the outer diameter was 1.8mm. At the same time, the silicone rubber was foamed by applying hot-airvulcanization. Thus, the insulating core member 101 was formed.

Thereafter, two parallel conductors 103, respectively comprising 0.5 mmφ of non-lead solder wire (tin-copper alloy, melting temperature at 217°C.) in which flux had been included at the center, were drawn at thesame tension and wound at winding pitch of 5 times/10 mm (4 times thewire diameter) in the length direction around the insulating core member101. As the final step, a mixture of ethylene copolymer serving as theinsulating cover 107 was extruded at temperature of 150° C., so that thesix protrusions 109, of which respective width was 0.6 mm and height was0.3 mm, and of which thickness was 0.3 mm, were provided. Thereafter,the cross-linking was done by applying electron beam thereto.

The thus obtained code type thermal fuse was cut at length of about 20cm, and each end of the insulating cover 107 was removed for about 1 cm.Then, lead wires having the nominal cross-sectional area of 0.5 mm²,each of which was at length of 100 mm, were connected via crimp-typeterminals, thus the code type thermal fuse assembly was manufactured.

Then, Experiments 1 and 2, substantially the same as those of the firstembodiment, were respectively done for the thus obtained code typethermal fuse, of which results are shown in FIG. 7.

EXAMPLE 8

The outer diameter of the insulating core member 101 was changed from1.8 mm to 2.2 mm. The other manufacturing method was substantially thesame as that of Example 7, thus the code type thermal fuse wasmanufactured. Then the experiments, substantially the same as those ofExamples 1 and 2, were done for this code type thermal fuse, of whichresults are also included in FIG. 7.

EXAMPLE 9

The outer diameter of the insulating core member 101 was changed from1.8 mm to 2.2 mm, and the height of each protrusion 109 was also changedfrom 0.3 mm to 0.5 mm. The other manufacturing method was substantiallythe same as that of Example 7, thus the code type thermal fuse wasmanufactured. Then the experiments, substantially the same as those ofExamples 1 and 2, were done for this code type thermal fuse, of whichresults are also included in FIG. 7.

EXAMPLE 10

There was no protrusion on the inner surface of the insulating cover107. The other manufacturing method was substantially the same as thatof Example 7, thus the code type thermal fuse was manufactured. Then theexperiments, substantially the same as those of Examples 1 and 2, weredone for this code type thermal fuse, of which results are also includedin FIG. 7.

According to results of FIG. 7, it is understood that the initialoperative temperature of each Example is the melting temperature of theconductor (217° C.).

With reference to the operative temperature after the lost of flux, itis understood that the operative temperature of the code type thermalfuse according to Examples 7 through 9 becomes lower, in which theinsulating core member 101, comprising the material havingcharacteristic of expanding in the circumferential direction, iscombined with the insulating cover 107 having the protrusions 109 on theinner surface. In particular, according to Example 8 in which the outerdiameter of the insulating core member 101 was enlarged, the operativetemperature was the lowest. This is because the space between theinsulating core member 101 and the protrusions 109 becomes narrower, andbecause the pressure against the conductor 103 becomes larger due toincrease of expanding volume of the insulating core member 101. Further,with reference to Example 9 in which the height of the protrusions 109was larger, the operative temperature was good, but as compared withExamples 7 and 8, the operative temperature was rather higher. This isbecause, as the protrusions 109 became larger, it became more difficultto transfer the heat from the outside to the conductor 103correspondingly, thus the heat sensitivity became poor. On the otherhand, with reference to the code type thermal fuse according to Example10 in which there was no protrusion 109 on the inner surface of theinsulating cover 107, the operative temperature became relativelyhigher. This is because, as there was no protrusion 109, it wasdifficult to apply pressure, generated by expansion of the insulatingcore member 101, to the conductor 103.

Now a fifth embodiment of the present invention will be explained withreference to FIGS. 8 and 9. There is an insulating core member 201,comprising a tensile resistant member 201 a and a cover member 201 b.The tensile resistant member 201 a was provided by applying siliconevarnishing to a glass code having the outer diameter of about 0.7 mm.Further, a compound of 100 w/t parts of silicone rubber, 1 w/t part offoaming agent (AIBN) and 2 w/t parts of organic peroxide cross-linkingagent kneaded on open roll, is used for the cover member 201 b. Then,the cover member 201 b is extruded in order to cover the periphery ofthe tensile resistant member 201 a, so that the cross-section of theouter diameter is 1.8 mm. At the same time, the silicone rubber isfoamed by applying hot-air vulcanization. Thus, the insulating coremember 201 is formed.

There are two parallel conductors 203 wound around the outer peripheryof the insulating core member 201 in the length direction. Eachconductor 203 comprises 0.5 mm φ of non-lead solder wire (tin-copperalloy, melting temperature at 217° C.) in which flux had been includedat the center, and two of which are drawn at the same tension and woundat winding pitch of 5 times/10 mm (4 times the wire diameter) in thelength direction around the insulating core member 201, so that theconductors 203 may dig into the insulating core member 201 sufficiently.

There is a fuse core 207, comprising a line-shaped insulator 205 woundaround the outer periphery of the conductor 203 in the length direction.As for the line-shaped insulator 205, a monofilament of 0.4 mm φpolyphenylene sulfide is used, and the line-shaped insulator 205 iswound in the length direction, reverse to that of the conductor 203, atwinding pitch of 10 times/32 mm (8 times the wire diameter).

The outer periphery of the thus obtained fuse core 207 is covered bytubular insulating cover 209. As for the insulating cover 209, a mixtureof ethylene copolymer serving has been extruded at temperature of 150°C., in a tubular shape having the thickness of 0.3 mm and the outerdiameter of 4.2 mm. Thereafter, the cross-linking is done by applyingelectron beam thereto, thus the code type thermal fuse according to thepresent embodiment is obtained.

The insulating core member 201 is formed by any material, havingcharacteristic of being not melted around the melting temperature of theconductor 203, and also characteristic of expanding in thecircumferential direction, for example, any metal wire to whichinsulation process has been applied, such as an electric wire in whichthermoplastic polymer or thermoset polymer has been extruded on aconductor, or cable material comprising any polymer which has beenformed by plastic extrusion of synthetic fiber, thermoplastic polymer orthermoset polymer, or any inorganic material such as ceramic fiber orglass fiber. Any one of the above materials may be used as a singlematerial, but it is also possible to use a plurality of materials bywinding the parallel conductors 3, or by stranding together, or bypreparing composite material through combination of different materialtypes.

As discussed above, among these materials according to the presentembodiment, with reference to the structure in which the tensileresistant member 201 a at the center is covered by polymer materialincluding the air serving as the cover member 201 b, it is possible toimprove the tensile strength and flexibility, and at the same time, itis also possible to arbitrarily control the degree of expansion of thecover member 201 b. Thus, this structure is particularly preferableamong others.

The tensile resistant material 201 a may be formed by using any knowntextile material. Further, a polymer material including the air, servingas the cover member 201 b, may have the structure that delomorphous oramorphous airtight spaces have been formed, preferably at least any partin the inside of polymer material comprising such as elastomer. Thereare various forming methods, for example, such as that polymer materialhas been mixed with organic foaming agent or inorganic foaming agent,and the mixture is heated and thus foamed, whereby the material havingisolated air holes can be formed. Further, it is also possible to useother forming methods, such as by including gas during extrusion moldingof polymer material, or forming of partially foamed material by addingsublimation material powder through heat-aging to polymer material, orforming of the airtight spaces, by preliminarily preparing polymermember having continuous holes in the length direction, and in thepost-process, by closing the continuous holes in the length direction.As for the polymer material as discussed above, it is possible to useany ordinary elastomer material, for example, silicone rubber, ethylenepropylene rubber, natural rubber, isoprene rubber, acrylic rubber,fluorocarbon rubber, ethylene-vinyl acetate copolymer (EVA),ethylene-ethyl acrylate copolymer resin (EEA), or any thermoplasticelastomer (TPE).

As for the conductor 203, it is possible to use, for example, metal thinwire selected from the group of low-melting point alloys and solder, orwire formed from conductive resin manufactured by filling high-densitymetal powder, metal oxide or carbon black, into thermoplastic resin suchas olefin resin or polyamide resin. The preferable wire diameter of theconductor 203 is substantially from 0.4 mm to 2.0 mm, because anordinary winding machine can wind such a conductor 203 around theinsulating core member 201 in the length direction. The conductor 203may be prepared by using a single conductor, or by using a plurality ofparalleled materials through application of the same tension thereto, orby using a plurality of stranded materials.

The line-shaped insulator 205 is formed by any material, havingcharacteristic of being not melted at the melting temperature of theconductor 203, for example, a wire material comprising any polymermaterial in which synthetic fiber, thermoplastic polymer or thermosetpolymer, such as aliphatic polyamide, aramid, polyethyleneterephthalate, wholly aromatic polyester or novoloid has been formed byplastic extrusion, or a wire material comprising any inorganic materialsuch as ceramic fiber or glass fiber. Any one of the above materials maybe used as a single material, but it is also possible to use a pluralityof materials by applying the same tension thereto, or by strandingtogether, or by preparing composite material through combination ofdifferent material types.

It is also possible to provide the line-shaped insulator 205 havingcharacteristic of contracting in the length direction around the meltingtemperature of the conductor 203. Accordingly, the line-shaped insulator205 may squeeze the conductor 203, whereby the disconnection of theconductor 203 may be done more securely. As for the line-shapedinsulator 205 having characteristic of contracting in the lengthdirection, it is possible to use, for example, any synthetic fiber suchas aliphatic polyamide, aramid, polyethylene terephthalate orpolybutylene terephthalate, or any fiber formed by high drawing of anyof these synthetic fibers, or any thermoplastic resin such aspolyethylene, polypropylene, aliphatic polyamide, polyethyleneterephthalate, propylene fluoroethylene, vinylidene fluoride orethylene-tetrafluoroethylene copolymer, which has been extruded in theshape of wire and drawn thereafter, or a wire material which has beenformed by annealing of synthetic resin, such as polyacetal, of whichcontracting rate is relatively large.

It is also possible to provide the line-shaped insulator 205 havingcharacteristic of expanding in the circumferential direction around themelting temperature of the conductor 203. Accordingly, the insulatingcore member 201 is expanded in the circumferential direction and pressesthe conductor 203 against the line-shaped insulator 205, and at the sametime, the line-shaped insulator 205 is also expanded and presses theconductor 203 against the insulating core member 201, and thesecharacteristics are preferable because the disconnection of theconductor 203 may be done more securely. As for the line-shapedinsulator 205 having characteristic of expanding in the circumferentialdirection, it is possible to use any material of which positiveexpansion coefficient is large, for example, foamed cross-linked rubber,or cross-linked rubber including any foaming material such as ADCA,exfoliated graphite or low-boiling liquid contained in micro capsule, orcross-linked rubber formed by knealing and incorporating relativelylow-boiling organic solvent in rubber, and after extrusion, formed byvaporizing the incorporated organic solvent by heat, or any materialwhich has been formed by blowing a high-compression gas at the same timeof extrusion molding of a synthetic resin, or a cross-linked rubber,which has been formed by adding heat sublimation material powder to anelastomer material, and thereafter, by heat sublimation of the addedpowder, or a cross-linked rubber, which has been formed by preliminarilypreparing elastic member having continuous holes in the length directionduring contour extrusion of elastomer material, and in the post-process,by closing the continuous holes in the length direction at predeterminedintervals through use of winding tension of the conductor, which will beexplained afterwards.

As there are various known materials and methods in regard to theinsulating cover 209, it is possible to select any appropriate materialand method from them, which can realize the working temperature lowerthan the melting temperature of the conductor 203. It is possible to usethe method, for example, in which a thermoplastic polymer such asethylene copolymer workable at relatively low temperature, or asynthetic rubber such as ethylene propylene rubber, styrene butadienerubber, isoprene rubber or nitrile rubber, is cross-linked by usinglow-temperature cross-linking method such as radiation cross-linking.Further, it is also possible to use a forming method by using siliconerubber which can be extruded around normal temperature and which can becross-linked at relatively low temperature. In particular, when thesilicone rubber is used, it is also possible to provide a braid asexterior element in order to reinforce the mechanical strength of theinsulating cover 209. The insulating cover 209 may be preferably thin,because of the increasing heat sensitivity, as long as the requiredcharacteristics such as the electric insulation ability and mechanicalstrength are satisfied.

The materials and numeric values as discussed above are mere examples ofthe embodiment, and it is possible to determine appropriately, accordingto using application, using purpose, using environment, etc.

Now a sixth embodiment of the present invention will be explained withreference to FIG. 10. There is a conductor 303, substantially the sameas that of the fifth embodiment as discussed above, around which aline-shaped insulator 305, also substantially the same as that of thefifth embodiment, is wound in the length direction at winding pitch of10 times/16 mm (4 times the wire diameter).

Thereafter, the conductor 303, around which the line-shaped insulator305 has been wound in the length direction, is also wound around aninsulating core member 301, substantially the same as that of the fifthembodiment, at winding pitch of 10 times/85 mm (6.5 times the wirediameter), thus a fuse core 307 is obtained. There is a tubularinsulating cover 309 covering the outer periphery of the fuse core 307.The material of the insulating cover 309 is substantially the same asthat of the fifth embodiment. Accordingly, a code type thermal fuseaccording to the present embodiment is obtained.

Now a seventh embodiment of the present invention will be explained withreference to FIG. 11. There is an insulating core member 401, formedfrom a compound of 100 w/t parts of silicone rubber, 1 w/t part offoaming agent (AIBN) and 2 w/t parts of organic peroxide cross-linkingagent kneaded on open roll. Then, this material for manufacturing theinsulating core member 401 is extruded, so that the cross-section of theouter diameter is 1.2 mm. At the same time, the silicone rubber isfoamed by applying hot-air vulcanization. Thus, the insulating coremember 401 is formed.

Thereafter, the insulating core member 401, a conductor 403 and aline-shaped insulator 405, both substantially the same as those of thefifth embodiment, are stranded together at pitch of 3.0 mm, thus a fusecore 407 is obtained.

There is a tubular insulating cover 409 covering the outer periphery ofthe fuse core 407. The material of the insulating cover 409 issubstantially the same as that of the fifth embodiment. Accordingly, acode type thermal fuse according to the present embodiment is obtained.

Now an eighth embodiment of the present invention will be explained withreference to FIG. 12. According to the eighth embodiment, there is abraid 505, substantially serving as the line-shaped insulator of thefifth embodiment. The other structure is substantially the same as thatof the fifth embodiment as discussed above, and the identical numeralsare allotted to the identical elements, and the explanation thereof willnot be made.

The fifth through eighth embodiments as discussed above have thefollowing merits. First, as the insulating core members 201, 301 and 401are expanded in the circumferential direction due to increase oftemperature, and presses the conductors 203, 303 and 403 against theline-shaped insulators 205, 305 and 405 or against the braid 505.Accordingly, the conductors 203, 303 and 403 can be disconnected moresecurely during melting of just before melting. Thus, even when theoriginal function of flux (the function to improve the detectingaccuracy) is deteriorated due to aging by heat, etc., it is stillpossible to maintain the good disconnection time. Further, it is stilleffective even when any deterioration, such as forming of oxide, appearson the surface of the conductors 203, 303 and 403 due to long-term usethereof and the melting disconnection cannot be done easily. Thus, it ispossible to further improve the operation reliability of the code typethermal fuse against deterioration by aging.

As the conductors 203, 303 and 403 are covered by the tubular insulatingcovers 209, 309 and 409, there are so much space around the conductors203, 303 and 403, that the conductors 203, 303 and 403 may be deformed.Accordingly, as the melted conductors 203, 303 and 403 are multipliedseparately, the disconnection of the conductors 203, 303 and 403 willnot be inhibited.

With reference to the fifth embodiment, there is an example, that theconductor 203 is wound around the insulating core member 201 in thelength direction, and that the other line-shaped insulator 205 is woundin the length direction reverse to that of the conductor 203. It is alsopossible, for example, to use a plurality of the line-shaped insulators205. Further, it is also possible to wind the line-shaped insulator 205and the conductor 203 in the same length direction, as long as thewinding pitch of the line-shaped insulator 205 is different from that ofthe conductor 203. It is also possible to add the line-shaped insulator205 directly along the longitudinal direction.

As for the conductor 203, for example, it is also possible to add theconductor 203 to the insulating core member 201 directly along thelongitudinal direction.

With reference to the sixth embodiment as discussed above, theexplanation is made as for an example of winding a single line-shapedinsulator 305 around the conductor 303 in the length direction, and thenwinding this unit around the insulating core member 301 in the lengthdirection. However, it is also possible, for example, to use a pluralityof line-shaped insulators 305, or to use a braid thereof, and it is alsopossible to use the conductor 303 and the line-shaped insulator 305stranded together. Further, it is also possible to wind the conductor303 around the line-shaped insulator 305 in the length direction. It isalso possible to wind the line-shaped insulator 305 around the conductor303 in the length direction, and to add it to the insulating core member301 directly along the longitudinal direction.

According to the fifth and six embodiments as discussed above, theexplanations are made as for examples of winding the conductors 203, 303or line-shaped insulators 205, 305 around the insulating core members201, 301 in the length direction. Further, according to the seventhembodiment, the explanation is made as for an example of stranding theinsulating core member 401, the conductor 403 and the line-shapedinsulator 405 together. It is also possible, for example, to use theconductor 203 wound around the insulating core member 205 in the lengthdirection, or to use the insulating core member 201 and the conductor203 stranded together in advance.

As discussed above, it is possible to provide various examples, but eachexample is essentially characterized in that, as illustrated in FIG. 9,at least a part of the fuse core 207 (307, 407) in the length directionhas the structure that the conductor 203 (303, 403) is sandwichedbetween the insulating core member 201 (301, 401) and the line-shapedinsulator 205 (305, 405 or the braid 505).

In this connection, the characteristic evaluation test was done forExample 11 corresponding to the fifth embodiment, Example 12corresponding to the sixth embodiment, and Examples 13 and 14corresponding to the seventh embodiment, of which explanation will bedone as follows.

For reference, according to Example 14, the line-shaped insulator 205was not used in regard to the fifth embodiment.

First, each of the code type thermal fuses according to Examples 11through 14 was cut at length of about 20 cm, and each end of theinsulating cover was removed for about 1 cm. Then, lead wires having thenominal cross-sectional area of 0.5 mm², each of which was at length of100 mm, were connected via crimp-type terminals, thus the code typethermal fuse assembly was manufactured.

Then, Experiments 1 and 2, substantially the same as those of the firstembodiment, were respectively done for the thus obtained code typethermal fuse, of which results are shown in FIG. 13.

According to the results of FIG. 13, it was confirmed that, in regard toExamples 11 through 13, as compared with Example 14 in which theline-shaped insulator was not used, the operative temperature becamelower, because of combination of the insulating core member, comprisingthe material having characteristic of expanding in the circumferentialdirection, with the line-shaped insulator.

Now a ninth embodiment of the present invention will be explained withreference to FIG. 14. According to the ninth embodiment, together withthe expansion of an insulating core member, an insulating cover iscontracted, whereby a conductor is disconnected, of which explanationwill be done as follows.

There is an elastic core 601 including the air, and the elastic core 601has a tensile resistant member 601 a at the center, around which iscovered by an elastic member 601 b including the air. A conductor 603 iswound around the elastic core 601, and an insulating cover 607 is woundaround the conductor 603. Thus, the elastic core 601 and the conductor603 serve as a fuse core 609. Further, the insulating cover 607 has atleast one or more (in the present embodiment, six) protrusions 611,formed continuously or intermittently on the inner surface in the lengthdirection.

The insulating cover 607 has characteristic of contracting in the inwardcircumferential direction, and the material thereof is not limited, aslong as the material belongs to pyrolysis polymer, and a plurality ofmaterial types may also be mixed with each other. It is possible to use,for example, any resin material such as polyester resin, polyamideresin, polyolefin resin (ethylene copolymer) or fluorocarbon resin, orany elastomer material such as nitrile rubber, ethylene propylenerubber, chloroprene rubber, acrylic rubber, silicone rubber orfluorocarbon rubber. According to the present embodiment, a mixture ofethylene propylene rubber with polyolefin resin (ethylene copolymer) atthe mixing rate of 1:1 has been prepared, with which additives such asfire retardant, antioxidant, lubricant, cross-linking aids, etc., havebeen further mixed.

The contracting speed of the insulating cover 607 can be adjusted bypyrolysis temperature. When the pyrolysis temperature is high (i.e. whenthe mixture has much material having high pyrolysis temperature), thecontracting speed will become lower. On the other hand, when thepyrolysis temperature is low (i.e. when the mixture has much materialhaving low pyrolysis temperature), the contracting speed will becomehigher. Therefore, it is possible to determine the speed appropriatelyaccording to the using condition.

The other structure is substantially the same as that of the fourthembodiment as discussed above, and the identical numerals are allottedto the identical elements, and the explanation thereof will not be made.

Now a tenth embodiment of the present invention will be explained withreference to FIG. 15. According to the tenth embodiment, with referenceto the ninth embodiment as discussed above, a space layer 605 comprisinga glass braid is provided on the outer peripheral side of the conductor603. The other structure is substantially the same as that of the ninthembodiment as discussed above, and the identical numerals are allottedto the identical elements, and the explanation thereof will not be made.

In this connection, the characteristic evaluation test was done forExamples 15, 16 and 17 corresponding to the ninth embodiment, andExample 18 corresponding to the tenth embodiment, of which explanationwill be done as follows. The structure of each Example is substantiallythe same as that of Example 7 corresponding to the fourth embodiment asdiscussed above, except for the insulating cover 607 of Example 15.

According to Example 16, with reference to Example 15, the elasticmember 601 b was not kneaded with foaming agent (AIBN), whereby theconductor 603 was disconnected only by contracting of the insulatingcover 607.

Further, according to Example 17, with reference to Example 15, aneutectic solder wire (melting temperature at 183° C.) at diameter of 0.6mm was used as the conductor 603.

First, each of the code type thermal fuses according to Examples 15through 18 was cut at length of about 20 cm, and each end of theinsulating cover was removed for about 1 cm. Then, lead wires having thenominal cross-sectional area of 0.5 mm², each of which was at length of100 mm, were connected via crimp-type terminals, thus the code typethermal fuse assembly was manufactured.

Then, Experiments 1 and 2, substantially the same as those of the firstembodiment, were respectively done for the thus obtained code typethermal fuse, and Experiment 3 as discussed below was also donerespectively, of which results are shown in FIG. 16.

Experiment 3: Constant Temperature Heating After Lost of Flux

Experiment Method:

As for the thus manufacture code type thermal fuse, flux was removedlikewise the case of Experiment 2. Thereafter, the temperature wasmaintained at 260° C., 280° C. and 300° C., respectively, and the timeuntil disconnection was measured.

According to the results of FIG. 16, it is confirmed that, withreference to the code type thermal fuse of the present embodiment, bymaintaining the elastic core 601 for a long time at a temperature (260°C.-300° C.) not higher than the operative temperature of the elasticcore 601, the insulating cover 607 is contracted, whereby the conductor603 is disconnected. When the elastic core 601 is maintained relativelyat higher temperature (260° C.-300° C.) which is not higher than theoperative temperature of the elastic core 601, the expanding motion ofthe elastic core 601 will not be facilitated, which would preventdisconnection of the conductor 603. Therefore, it is confirmed that thecontracting motion of the insulating cover 607 is considerablyeffective.

According to the ninth and tenth embodiments as discussed above, theprotrusions are provided on the inner periphery of the insulating cover607. However, it is possible to provide the insulating cover 607 withouthaving the protrusion.

INDUSTRIAL APPLICABILITY

The present invention relates to the code type thermal fuse and a sheettype thermal fuse, which can be disconnected when any part thereof isexposed in an abnormal high temperature state, so that the abnormaltemperature can be detected. More particularly, the present inventionrelates to the code type thermal fuse and the sheet type thermal fuse,of which disconnection time is still good even after being deteriorateddue to aging by heat, and which has good operative reliability. Thepresent invention may be used for various purposes, for example,refrigerators, indoor and outdoor equipment of air conditioners, clothdrying machines, rice cookers with keep-warm function, hot plates,coffee brewers, water heaters, ceramic heaters, oil heaters, automaticdispensers, electric blankets, floor heating panels, copying machines,facsimile machines, dishwashers, fryers, etc.

1. A code type thermal fuse comprising: a fuse core produced by windinga conductor meltable at a predetermined temperature on an insulatingcore member continuously provided in the length direction; and aninsulating cover covering the outer periphery of said fuse core,characterized in that: said conductor can be cut by expanding saidinsulating core member at a predetermined temperature and/or bycontracting said insulating cover at said predetermined temperature. 2.The code type thermal fuse as claimed in claim 1, further characterizedin that: said insulating core member has at least one or moreprotrusions formed continuously or intermittently in the lengthdirection on the outer periphery of said insulating core member.
 3. Thecode type thermal fuse as claimed in claim 1, further characterized inthat: said insulating cover has at least one or more protrusions formedcontinuously or intermittently in the length direction on the innerperiphery of said insulating cover.
 4. The code type thermal fuse asclaimed in claim 1, further characterized in that: another line-shapedor braid-shaped insulator is provided on the inner peripheral side ofsaid insulating cover; and said conductor is sandwiched between saidinsulating core member and said line-shaped or braid-shaped insulator atleast partially in the length direction of said conductor.
 5. The codetype thermal fuse as claimed in claim 4, further characterized in that:said line-shaped or braid-shaped insulator has a characteristic ofcontracting in the length direction around a melting temperature of saidconductor.
 6. The code type thermal fuse as claimed in claim 4, furthercharacterized in that: said line-shaped or braid-shaped insulator has acharacteristic of expanding in the peripheral direction around a meltingtemperature of said conductor.
 7. The code type thermal fuse as claimedin claim 1, further characterized in that: said insulating core membercomprises a gas-containing material as a structural element.
 8. The codetype thermal fuse as claimed in claim 7, further characterized in that:said insulating core member comprises a gas-containing material coveringa periphery of a tensile resistant member at the center of saidinsulating core member.
 9. A sheet type thermal fuse, comprising: thecode type thermal fuse according to claim 1, provided on a flat surfacein a serpentine manner; and means for fixing a layout of said code typethermal fuse.
 10. The code type thermal fuse as claimed in claim 2,further characterized in that: said insulating cover has at least one ormore protrusions formed continuously or intermittently in the lengthdirection on the inner periphery of said insulating cover.
 11. The codetype thermal fuse as claimed in claim 2, further characterized in that:said insulating core member comprises a gas-containing material as astructural element.
 12. The code type thermal fuse as claimed in claim3, further characterized in that: said insulating core member comprisesa gas-containing material as a structural element.
 13. The code typethermal fuse as claimed in claim 4, further characterized in that: saidinsulating core member comprises a gas-containing material as astructural element.
 14. The code type thermal fuse as claimed in claim5, further characterized in that: said insulating core member comprisesa gas-containing material as a structural element.
 15. The code typethermal fuse as claimed in claim 6, further characterized in that: saidinsulating core member comprises a gas-containing material as astructural element.
 16. A sheet type thermal fuse, comprising: the codetype thermal fuse according to claim 2, provided on a flat surface in aserpentine manner; and means for fixing a layout of said code typethermal fuse.
 17. A sheet type thermal fuse, comprising: the code typethermal fuse according to claim 3, provided on a flat surface in aserpentine manner; and means for fixing a layout of said code typethermal fuse.
 18. A sheet type thermal fuse, comprising: the code typethermal fuse according to claim 4, provided on a flat surface in aserpentine manner; and means for fixing a layout of said code typethermal fuse.
 19. A sheet type thermal fuse, comprising: the code typethermal fuse according to claim 5, provided on a flat surface in aserpentine manner; and means for fixing a layout of said code typethermal fuse.
 20. A sheet type thermal fuse, comprising: the code typethermal fuse according to claim 6, provided on a flat surface in aserpentine manner; and means for fixing a layout of said code typethermal fuse.